Sorry to say but you were robbed in those 400 rds.
Portuguese ammo headstamp is "FNM", circled NATO cross, Year-batch.
Unfortunately, given the Port ammo good reputation, there are dealers who are selling it mixed with ammo from other sources. Usually it was with singaporean. In your case, You were really unlucky there. FAMAE is chilean and contrarily with the rifles they make, their ammo is the reference of what you shouldn't buy. The worst of worst. Before you buy portuguese ammos check if the boxes say "DATA" (the Portuguese word for date). "FECHA" is Spanish. FNM sometimes may come with the INDEP brand (it's the holding company of FNM).
Here are pics taken by a guy who bought a 1,000 rds wooden crate of portuguese FNM ammo from AIM. Yours should look like this (some crates are painted in olive drab):
http://www.millenicom.com/~patriot/M1A/ammo/portuges.htm
As to the FNM ammo itself, from what i've been reading around in boards (falfiles.com, assaultweb.net, combatrifles.com) the general opinion is that this is the best surplus ammo in the market. It's accurate, clean and you get consistent groups with it. Years ago, Soldier of Fortune tested it and said it's the sole mil surplus round equal to match grade. Some even say it's superior to Lake C. match. Many guys say they've fired thousands of rounds with 0% problem.
Some dealers sold out all they had, but AIM still has them:
http://198.63.62.70/acatalog/AIM_Rifle_Ammunition_8.html
cheers